This invention relates to a vehicle occupant protection apparatus for protecting the neck of an occupant seated in a vehicle seat.
Normally, between the headrest at the top of a vehicle seat and the neck of an occupant seated in the seat, there is a so-called behind-the-neck gap. When a vehicle is impacted from behind by an impacting body (hereinafter called a xe2x80x9crear-end collisionxe2x80x9d), as a reaction to this the upper body of the occupant falls backward. And the larger is the behind-the-neck gap, the greater is the load which acts on the neck of the occupant.
As technology for lightening the load on the neck, there has been that in which the cushioning capacity of the seat back is raised. When the upper body of the occupant falls backward, because a seat back with a large cushioning effect compresses greatly, the behind-the-neck gap decreases and the load on the neck is lightened. However, when the cushioning effect of the seat back is too large, ride comfort may decrease. To avoid this, technology aiming to achieve both ride comfort and protection has been developed, as shown in FIG. 13 and FIG. 14A through 14C.
An occupant protection apparatus shown in FIG. 13 has a headrest 103 mounted swingably front/rearward by way of a swinging mechanism 102 to the top of a seat back 101 of a seat 100.
When as a reaction to the vehicle suffering a rear-end collision the upper body of an occupant 104 falls rearward, an external force W1 acts on the seat back 101 from the upper body. The swinging mechanism 102 swings under this external force W1, and the headrest 103 consequently advances from a normal position shown with broken lines to the position shown with solid lines. And by a behind-the-neck gap 105 between the neck of the occupant and the headrest 103 becoming small in this way, the load on the neck is lightened.
A seat 200 provided with an occupant protection apparatus shown in FIG. 14A has a seat cushion 201, a hinge mechanism 202, a seat back 203 attached swingably front/rearward to the seat cushion 201 by way of this hinge mechanism 202, and a headrest 204 attached to the top of the seat back 203.
The hinge mechanism 202 is made up of a fixed plate 211 attached to the rear end of the seat cushion 201, a first swing arm 214 attached swingably up/downward to the fixed plate 211 by way of a first link 212 and a second link 213, and a second swing arm 215 attached swingably front/rearward to the first swing arm 214. The seat back 203 is attached to the distal end of the second swing arm 215. The swing angles of the first swing arm 214 and the second swing arm 215 correspond to size of an external force.
From the state shown in FIG. 14A, the first swing arm 214 and the second swing arm 215 will swing counter-clockwise in the figure under the impact force of a rear-end collision. As a result, because the seat back 203 temporarily moves toward the upright, as shown in FIG. 14B, a behind-the-neck gap 221 decreases. After that, due to the upper body of an occupant 222 falling rearward as a reaction to the rear-end collision, an external force acts on the seat back 203 from the upper body. And under this external force, as shown in FIG. 14C, the seat back 203 and the second swing arm 215 fall rearward. As a result, the impact acting on the occupant 222 is absorbed by the seat back 203, and the behind-the-neck gap 221 decreases further. In this way it is possible to make the behind-the-neck gap 221 small and moderate the impact which acts on the neck.
However, the two related art technologies described above, as shown in FIG. 13 and FIGS. 14A through 14C, are passive vehicle occupant protection apparatus, which commence operation when an external force acting at the time of rear-end collision reaches a preset fixed reference value.
Consequently, when the reference value for operation commencement is too large, in the case of a light collision with a small impact energy, the vehicle occupant protection apparatus cannot operate. And, when the upper body of an occupant falls rearward as a reaction to a rear-end collision, the external force which acts on the seat back from the upper body varies depending on the weight of the occupant. When the occupant of the seat is light, the reference value for actuation commencement may not be reached.
When on the other hand the reference value for operation commencement is too small, there is a risk that the vehicle occupant protection apparatus may operate even in the normal state, when there has been no rear-end collision. Thus, there is room for improvement in the protection apparatus of related art described above. That is, there is a need to more certainly lighten the load on the neck of an occupant seated in a vehicle seat when the vehicle is collided with by an impacting body from behind (suffers a rear-end collision).
The present invention provides a vehicle occupant protection apparatus including a headrest mounted movably front/rearward to the top of a vehicle seat, a headrest actuating mechanism for moving the headrest forward, and a headrest control unit for drive-controlling the headrest actuating mechanism, wherein the headrest control unit includes impact predicting means for predicting the impact of an impacting body on the vehicle from behind and drive-controls the headrest actuating mechanism on the basis of a prediction signal from this impact predicting means.
That is, an active vehicle occupant protection apparatus can be constructed which controls the operation of a headrest actuating mechanism to commence on the basis of predicting itself that an impacting body is about to impact the vehicle from behind. Accordingly, when a rear-end collision is predicted by the impact predicting means, in correspondence with a prediction signal outputted from the impact predicting means, a control signal is issued to the headrest actuating mechanism from the headrest control unit, and the headrest is moved forward by the headrest actuating mechanism. Consequently, at the rear-end collision prediction stage, the gap between the headrest at the top of the seat and the neck of the occupant seated in the seat is forcibly reduced in advance. And by the behind-the-neck gap being reduced like this immediately before the rear-end collision, the load acting on the neck of the occupant when the upper body of the occupant falls rearward as a reaction to the rear-end collision can be more certainly lightened.
Preferably, the impact predicting means includes relative speed detecting means for detecting the relative speed of the impacting body with respect to the vehicle and the headrest control unit controls the headrest actuating mechanism to increase the amount of forward movement of the headrest in correspondence with a detection signal from the relative speed detecting means. In this case, when an impact is predicted by the impact predicting means, in correspondence with the relative speed of the impacting body with respect to the vehicle, the amount of forward movement of the headrest can be varied more suitably. When there has been a rear-end collision, as a reaction to this the upper body of the occupant tends to fall rearward. The amount of this falling is larger the larger is the relative speed. In this invention, the larger is the relative speed, the more the amount of forward movement of the headrest is increased. Consequently it is possible to make the behind-the-neck gap smaller immediately before the impact, and the load acting on the neck of the occupant when as a reaction to the rear-end collision the upper body of the occupant falls rearward can be rapidly and certainly lightened.
Preferably the seat in this invention has a seat back deformation detector for detecting deformation of a seat back deforming in accordance with the size of a rearward external force acting on the seat back, and the headrest control unit controls the headrest actuating mechanism to increase the amount of forward movement of the headrest in correspondence with a detection signal from the seat back deformation detector. That is, when there has been a rear-end collision, as a reaction thereof the upper body and the head of the occupant fall rearward. Because the upper body is supported by the seat back, the amount by which it falls is relatively small. On the other hand, immediately before the rear-end collision the head is away from the headrest. Consequently, the amount by which the head falls is greater than the amount by which the upper body falls. This tendency is more marked the greater is the impact energy.
As a result of the upper body of the occupant falling rearward as a reaction to a rear-end collision like this, an external force acts on the seat back from the upper body. In correspondence with this external force the seat back deforms. The greater is the impact energy the greater is the external force, and consequently the greater is the deformation of the seat back. In this invention, the greater is the deformation of the seat back, the more the amount of forward movement of the headrest is increased. Because of this, the behind-the-neck gap can be made smaller at the time of a rear-end collision. Consequently, when the upper body of the occupant falls rearward as a reaction to a rear-end collision, the load acting on the neck of the occupant can be lightened more rapidly and certainly.
Also, preferably, the headrest actuating mechanism of this invention has a headrest actual forward movement detector for detecting the actual forward movement of the headrest, and the headrest control unit controls the headrest actuating mechanism to reduce the speed of forward movement of the headrest as the actual forward movement detected by the headrest actual forward movement detector increases. That is, as the headrest moves forward, as the behind-the-neck gap decreases, the headrest slows as it moves forward. And accordingly, even if the advancing headrest hits the neck, the load which acts on the neck is extremely slight.